Fix text alpha updates during fade

test/runtime/rendering/runtime_component_test.dart

@@ -138,6 +138,51 @@ void main() {
       );
     });
 
+    test('updates text alpha style without rebuilding text component', () {
+      final component = RuntimeComponent(
+        node: const RuntimeNode(
+          id: 'text',
+          type: RuntimeNodeType.text,
+          text: 'Fade me',
+          alpha: 0,
+          color: Color(0xffffffff),
+        ),
+        resources: GameResourceManager(),
+        onNodeTap: (_, __) {},
+      );
+
+      final text = component.children.whereType<TextComponent>().single;
+      expect(((text.textRenderer as TextPaint).style.color!).a, 0);
+
+      component.setRuntimeAlpha(1);
+
+      final updatedText = component.children.whereType<TextComponent>().single;
+      expect(identical(updatedText, text), isTrue);
+      expect(((updatedText.textRenderer as TextPaint).style.color!).a, 1);
+    });
+
+    test('updates button text alpha style without rebuilding text component', () {
+      final component = RuntimeComponent(
+        node: const RuntimeNode(
+          id: 'button',
+          type: RuntimeNodeType.button,
+          text: 'Fade me',
+          alpha: 0,
+        ),
+        resources: GameResourceManager(),
+        onNodeTap: (_, __) {},
+      );
+
+      final text = component.children.whereType<TextComponent>().single;
+      expect(((text.textRenderer as TextPaint).style.color!).a, 0);
+
+      component.setRuntimeAlpha(1);
+
+      final updatedText = component.children.whereType<TextComponent>().single;
+      expect(identical(updatedText, text), isTrue);
+      expect(((updatedText.textRenderer as TextPaint).style.color!).a, 1);
+    });
+
     test('applies text shadow style', () {
       final component = RuntimeComponent(
         node: const RuntimeNode(